Let us set up the equation using the given information
Boys = x
Girls = √x
Boys + girls = 42
Equation: x + √x = 42
You can now work out this equation to solve for x, OR reason your way through it. By substituting numbers into the equation. Try 36
36 + √36 = 42
36 + 6 = 42
42 = 42
ANSWER: 36 Boys (and 6 girls)
Hope this helps! God bless!! :)